Foreigner

Foreigner allows Drupal to maintain references to content items and users that are managed externally, and to treat these references like regular Drupal nodes/users.

The module supports a simple URI approach for identifying foreign items and users. Using a single delimiter that you configure, you may use identifiers of an arbitrary number of components to identify your items and users, in a hierarchical fashion. For instance, you might identify a content item as:

myworld:myapp:items:123

and a user as:

myworld:myapp:users:joe_schmoe

Foreigner provides functions that check whether a given item or user URI is already known, and then return an internal Drupal identifier (nid or uid) for the item or user, after having created that item or user if necessary. Additionally, Foreigner parses out the hierarchy implicit in the URI, and maintains a mapping of that hierarchy, so that you will be able to query for "all users in myworld:myapp" or "all items in myworld:myapp", and so on.

This code is not yet complete.